The invention relates to a laundry dryer having a drying chamber for the articles to be dried and having a process air channel, in which are located a fan for driving process air through the drying chamber and a heat exchanger arrangement, which can extract heat from the process air flowing out from the drying chamber and can supply heat to the process air flowing into the drying chamber, the process air channel having a supply air opening for drawing in process air from the surroundings of the laundry dryer, an exhaust air opening for expelling process air to the surroundings of the laundry dryer and an exhaust air channel part, through which process air can be conducted to the exhaust air opening and which has a distributor, by way of which condensate, which has been separated off from the process air in the heat exchanger arrangement, can be distributed in the process air flowing through.
The invention also relates to a method for operating such a laundry dryer.
Such a laundry dryer and such a method appear in the non-prepublished German patent application 10 2007 011 809.2 and the similarly non-prepublished international patent application PCT/EP2008/052259 parallel thereto. In the laundry dryer described there the heat exchanger arrangement can be a simple heat exchanger or heat pump.
A laundry dryer with heat recovery appears in DE 30 00 865 A1. This describes what is known as an exhaust air dryer, which heats an air flow in an open channel once and passes it through the laundry to be dried, then expels it from the channel. The heat recovery takes place by means of a simple heat exchanger, in which heat from the process air to be expelled is transferred to newly inflowing process air. The process air heated in the heat exchanger is heated further by means of a heater and then reaches the laundry items to be dried.
A laundry dryer appears in WO 2004/059070 A1 having an atomizer, in particular an ultrasonic nebulizer, which can be used to distribute a fluid in the process air supplied to the articles to be dried or treated.
Generally a laundry dryer is operated in the manner of an exhaust air dryer or a condensation dryer. An exhaust air dryer conducts heated air once through the laundry to be dried and discharges this moisture-laden air through an exhaust air hose from the exhaust air dryer and out of the room in which it is located. A condensation dryer, the mode of operation of which is based on the condensing of the moisture evaporated from the laundry by means of warm process air, does not require an exhaust air hose and allows energy to be recovered from the heated process air, for example by using a heat pump. However with such a condensation dryer it is generally necessary to collect the condensate occurring and either pump it away or dispose of it by emptying collecting vessels manually.
A laundry dryer with a heat pump circuit is described in DE 40 23 000 C2, being configured essentially as a condensation dryer and wherein a supply air opening is arranged in the process air channel between a condenser and an evaporator in the heat pump circuit, it being possible to close off said supply air opening with a controlled sealing facility.
With an exhaust air dryer the air, which is moisture laden after passing through the drum containing the laundry items, is generally conducted from the dryer. Compared with a condensation dryer an exhaust air dryer is simpler and therefore cheaper to construct. During operation an exhaust air dryer draws air from its surroundings and uses it directly for drying purposes.
As described in DE 30 00 865 A1, heat recovery is also possible in principle in an exhaust air dryer but such heat recovery involves a certain cooling of the air, in which process condensate can be precipitated from the exhaust air and would have to be disposed of. Ambient air (at for example 20° C. and 60% relative air humidity; known as supply air) flows over heat exchanger surfaces of the air/air heat exchanger and is heated there as the warm process air coming from the drying chamber is cooled. Depending on the cooling output or heat exchange, condensate occurs which is collected in a vessel or pumped away. In the first instance emptying is necessary and in the second instance a connection to the waste water network. The amount of condensate occurring is a measure of the thermal energy emitted in the heat exchanger and therefore a measure of the energy efficiency improvement.
To dispose of condensate occurring during a drying process and without the need for interim storage and otherwise disposing of the condensate, according to the non-prepublished patent application cited above provision is made for conducting some of the process air to be discharged from the dryer past the heat exchanger arrangement and by way of an evaporator, to which evaporator the condensate occurring is supplied, so that it evaporates in the process air flowing over it and can be discharged with this. However this necessarily means that some of the heat present in the air to be discharged is no longer available to be recirculated to the drying process.